--- a/src/cx/tree.h	Wed Dec 31 14:58:52 2025 +0100
+++ b/src/cx/tree.h	Wed Dec 31 15:11:12 2025 +0100
@@ -59,6 +59,9 @@
     struct cx_tree_visitor_queue_s *next;
 };
 
+/**
+ * An iterator (DFS) or visitor (BFS) for a tree.
+ */
 typedef struct cx_tree_combined_iterator_s {
     /**
      * Base members.
@@ -334,6 +337,7 @@
  * Structure for holding the base data of a tree.
  */
 typedef struct cx_tree_s {
+    /** Base attributes. */
     CX_COLLECTION_BASE;
     /**
      * A pointer to the root node.